DWI is an acronym that applies to the operation of motor vehicles and a violation of driving laws. DWI stands for driving while intoxicated or driving while impaired. DUI, or driving under the influence, is another acronym sometimes used for the same violation. Every jurisdiction in the United States has a law that prohibits drivers from operating their vehicle under the influence of alcohol.
A DWI offense applies when a driver is stopped by law enforcement and found to have a blood alcohol level at or above the legal limit. The legal blood alcohol concentration (BAC) level is .08, or 8 grams of alcohol per 100 deciliters of blood. Any driver who is stopped for erratic driving or whom an officer suspects has been drinking can be asked to take a breath test or blood test. Refusal of a test for a potential DWI offense is the same as admission of guilt.
During a DWI investigation, once law enforcement has stopped a suspected driver, a field sobriety test will be administered. Field sobriety tests in suspected DWI stops might include a heel-to-toe walk in a straight line, standing on one foot, reciting a portion of the alphabet, and other tasks requiring mental and physical coordination. If a driver fails a field sobriety test, he or she is usually asked to breathe into a preliminary screening device commonly known as a breathalyzer.